According to the prior art, electrical steel in coil form is available in widths up to 48 inches. Motor or generator cores have a stator and a rotor, each formed from a plurality of stacked laminations referred to also herein as lamination layers. Coil form widths of up to 48 inches allows for stator production in a complete round form up to that size. For larger stators, like those typically seen in large generator or motor applications, each of the lamination layers of the stator must be produced in an arc segment form with typically 6 or 8 lamination segments 10 (FIG. 1) making up the complete stator lamination layer.
Currently the following prior art process steps are known for a segmented stator lamination layer (see FIG. 1 for one of the segments).
As shown in FIG. 1, material is slit to form a strip 61 having a width 11 required based on part and die designs. For this example, the material strip width 11 is 32.875 inches which is a segment width 9 of 32.480 inches plus 0.1975 inches in each scrap web 8A, 8B, and has an arc angle 12 of 60°.
Stator lamination segments 10 are produced in either a progressive or compound die that is mounted in a punch press. The material progression distance 7 as shown in FIG. 1 required to produce each part in this example is 13.050 inches. Note the overlap because of the bottom curved edge on segment 10 and upper curved edge on subsequent segment 10A. Total material required to produce one lamination layer of six stator lamination segments is 32.875 inches×13.050 inches×6=2574 square inches.
The six stator lamination segments 10 are assembled into a stator core by placing the six lamination segments 10 per laminate layer in a circular pattern on an assembly fixture. Each subsequent layer of lamination segments is rotated 30 degrees to offset the split lines between the lamination segments in each lamination layer.
The assembled stator core is fused together via welding. Some designs may also use tie rods and/or a combination of tie rods and welding to fuse the core.
For a first option for making a rotor lamination according to the prior art, the following steps are provided.
Material 13 is slit to a width 5 required based on the part and die designs (see FIG. 2). For this example the material width 5 is 40.530 inches as shown in FIG. 2, which is the rotor width 4 of 40.157 inches plus a scrap width at 3A, 3B of 0.1865 inches each.
Rotor blanks (see FIG. 4) are produced in a compound die which finishes the ID 14 and the OD 27 of the part. The material progression 28 required to produce each part in this example is 40.350 inches, which is the rotor width of 40.157 inches plus a 0.0965 inch scrap width for each scrap segment 29A, 29B. Total material required to produce one rotor lamination is 40.530 inches×40.350 inches=1635 square inches.
The rotor slots 15 as shown in FIG. 5 are then added to the rotor blank. This can be done in a notching press with a notching die which produces 1-2 slots per stroke while indexing the lamination on their central axis. A single stroke press of higher tonnage capacity can also be used to punch all of the slots at once with a die produced for this press. In both cases the laminations are generally manually loaded into the machine, although this process can be automated.
The rotor core is assembled on an assembly mandrel and locked together with a process similar to that used in stator assembly.
Steps for making a rotor lamination according to a second option according to the prior art are as follows.
Material is slit to the width required based on the part and die designs. For this example the material width 5 is 40.530 inches as shown in FIG. 2, which is the rotor width 4 of 40.157 inches plus 0.1865 inches scrap for each scrap web 3A, 3B.
Slit material 13 is sheared to a length of 40.530 inches (slightly larger than what is shown in FIG. 2) producing a square of that size. Total material required to produce one rotor lamination for this second option is thus 40.530 inches×40.530 inches=1643 square inches.
The ID 14 of the rotor is punched in a manually fed single hit operation as shown in FIG. 2.
The square blank for the second option with punched ID is loaded into a circle shear to produce a round blank of a slightly larger OD 30 of 40.3 inches as shown in FIG. 3 than the diameter 31 of 40.157 inches of the finished rotor as shown in FIG. 4.
The rotor slots 15 are added in the same manner as described in the first option process. The rotor OD 30 is also trimmed to a final size 31 of 40.157 inches in this operation (see prior art FIG. 4).
Rotor cores are assembled on an assembly mandrel and locked together with a process similar to the process used in stator assembly.
Total material usage for the above processes are 4209 square inches and 4217 square inches respectively dependent on which rotor process option one or option two is used. Subtle variations in the above processes are likely to exist but they would have little or no impact on the overall material usage.